16alpha-methylpregnane derivatives and processes for preparing the same



-16ot-METHYLPREGNANE DERIVATIVES AND PROCESSES FOR PREPARING THE SAME Earl M. Chamberlin, Westfield, John M. Chemerda, Me-

tuchen, Jan Ten Broeke, Rahway, and Edward W. Tristram, Cranford, N.J., assignors to Merck & Co. Inc., Rahway, N.J., a corporation of New Jersey No Drawing. Filed Nov. 13, 1957, Ser. No. 696,030

7 6 Claims. (Cl. 260-397.45)

invention relates to the preparation of 304,21- diacyl 11a alkyl 11 3,17a dihydroxy pregnan 20- one. It is also concerned with the preparation of novel chemical compounds produced as intermediates in the synthesis of 3a,2l-diacy1-1'6a-alkyl-11fi,17a-dihydroxypregnan-ZO-one.

.Thenew chemical compounds with which this -inven-- tion is concerned,-3a,21-diacyl-l6u-alky1-1113,17a-dihydroxy-pregnan-ZO-orie can be readily converted to 160:- alkyl 1711,21 dihydroxy 4 pregnene 3,11,20 trione and 16a -alky1 11/3,17oc,21 trihydroxy 4 pregnene- 3,20-dione'compounds which possess .marked and enhanced anti-arthritic properties when compared with the physiologically active cortical hormones 17a,2l-dihydroxy 4 p'regnene 3,11,20 trione 11B,l7a,21 trihydroxy-4-pregnene-3,ZO-dione;

In preparing the novel chemical compounds of the present invention, we utilize as the starting material 31:-

Patented May 2, 1961.

2 with alcoholic alkali metal hydroxide to form l6a-alky 3a-hydroxy-1l-oxo-l7(20)-pregnen-21-oic acid having the following structural formulawherein R is as above.

The 160: alkyl 3oz hydroxy l1 oxo 17(20)- pregnen-Zl-oic acid thus formed is reacted with an esterifying agent such as diazomethane to form l6u-alkyl- 3a-hydroxy-l1-oxo-l17(20)-pregnen-21-oic acid alkyl ester which may be identified by the structural formulaacyloxy-l6a-alkylpregnane-1i1,20-dione which has the following structural formuladihalo-pregnerne-ILZO-dione which may be identified by r the following formulawherein R and R V chlorine. v I p V The 3a 7 acyloxy' 161x alkyl l7a,21 dihalo pregnaue-11,20-dione preparedas described above is reacted are as above and X is bromine or Y COOR' wherein R is as above. 7

The low-alkyl 3a hydroxy pregnen-Zl-oic acid alkyl ester thus obtained is reduced with lithium aluminum hydride to form ,16ot-alkyl-l7(20)- pregnen-3d,1lfl,21-triol, which may be represented by thefollowing structural formular wherein R is as above. l

Acylation of the latter compound; namely, loot-alkyl- 'formulaonion Hydroxylation of the 3a,2 l-diacyloxy-16d-alkyl-17 (20)-='. pregnen-ll-ol with osmium tetroxide under oxidizing conditions results' in the formation of l6 a-alkyl-3u,l-lfl,.i

- 111 oxo l7(20)-' 1Ia-21-tetrahydroxy-pregnan-20-one which has the structural formula- CHzOH wherein R and R' are as above.

The 16:: alkyl 30:,11B,17bc,21 tetrahydroxy pregnan-ZO-one prepared as above may be readily converted to 160:. alkyl 170;,21 dihydroxy 4 pregnene 3,11, -20-trione in the following manner.

The 16a-alkyl-3a,1 1 p, 17 u,2l-tetrahydroxypregnane-ZO- one is reacted with N-bromo-acetamide. to form-16cc-alkyl- 17a,21-dihydroxypregnane-3, 11,20-trione. Acetylation. of they latter compound with acetic anhydride in pyridine. results inthe: formation: of 16OL-a1kyl-170t,21-dlhYdIOXypregnane.-3,1l,20-trione 21-acetate. The latter-compound. is reacted with bromine in glacial acetic. acid-chloroformto produce 16a-a1kyl-4-bromo-17m2l-dihydroxy-pregnan- 3,11,20-trione ZI-acetate which is then reacted with semicarbazide to form 16a-a1kyl-17a,2l-dihydroxy-4-pregnen- 3,11,20-trione 3,20-bis-semicarbazone is reacted with potassium bicarbonate. or potassium: hydroxide in aqueous methanol to form 16a-a1kyl-17a,21-dihydroxy-4-pregnenc- 3,11,20-trione 3,20-bis-semicarbazone which is thenhydrolyzed under acid conditions to produce 16a-alkyl-17a, 21 dihydroxy-4-pregnene-3,11,20-tri0ne; this compound is esterified to produce the corresponding-: 21-ester derivatives The following experimental part illustrates in detail some of the compounds which constitute invention and methods for their production- However, the invention is not to be construed: as limited thereby 'in; spirit-or v by dissolving in methylene chloride and adding methanol.

in scope since it will be apparent to' those skilledin the artthatmany modifications in materials and. methods may be made without departing from the invention.

Preparation of 3oc-acet0xy-1 :,21-dibromo-16a-methyl pregnane-I 1,20-dione bromoe1 6wmethylpregnanmll,20-dione, recrystallized Wa etv n ex racte with her.

M.P. 227 C. (decomposure)- Analysis calculated for C H O Br -Br, 29.26. Found:

The 3u-acetoxy-16a-methylpregnane-11,20-dione employed as a starting material in this example may. beprepared by reacting. 3a-acetoxy-l6-pregnene-1.1,20-dione withmethyl magnesium iodide in the presence of. cuprous chloride.

Preparation of 3u-hydroxy-16a-methyl-1 Lam-17(20)- pregnen-ZI-oic acid 3.0- g. of 3a-acetoxy 17a,2l-dibromo-16a-methylpregnan-11,20-dione is dissolved in 20 m1. of ethanol and refluxed for 1 hour with a solution of 12 g. of potassium hydroxide in 2 0 ml. of water. The cooled, two phase reaction mixture is poured into 200 m1. of waterland 6X1. The ethereal extract" tracted'zwith 3x100 mlof ether. is washed with water and dried with sodium sulfate. The

ether is evaporated to a volume of. approximately 20ml! Upon cooling, 3a-hydroxy-16a-methyl-11-oxo-17'(20)* pregnen-Zl-oic acid crystallizes from solution. After w frigeration, the product is filtered and washed with a littleether; 0.89 g. (4 4%); M.P. 215-223;

Preparation of methyl 3a-hydraxy-I6a-rnethyl-lloxo- 1 7 (20) -pregnen-21.-oate.

0.83 g. of '3a-hydroxy-16u-methyl-1 1-oxo-17 (20) -pregne1r-21-oic: acid. is suspended in 200 ml. of ether and stirred overnight with excess diazomethane. The ether is removed ir'rvacuo and the residue is dissolved ina mixture: of hot n hexane and acetone.

IR. spectrum, 2.8-3.0 ,LL '(OH); 5.87 1:. (carbonyl); 6.06 n (double bond).

Preparation of 16a-methyl-17(20)-pregnene- 3a,1 1 3,21-triol I decomposed by the addition of 500 ml. of ether saturated 3 with, Water. An additional 1 00 ml..of water andj ml'. of'2L5 Nhydrochloric, acid is added. The aqueous layer is removed and the ether layer washed with water and dried with sodiumsulfate. Evaporation, of the ether leaves. a crystalline residue of 16a-methyl-17(2O)-preg.-

nene-3a,11 3,21'-triol; 6.86 g.; M.P. 153-163. A. sample recrystallized fromether, petroleum ether melted 161"- x332 no max.

LR. 3.02 y. (hydroxyl), 5.98 t (double bond), no carbonyl. Analysis calculated for C H 5O3C, 75.81; H, 10.41.

Found: C, 76.14; H, 10.60.

Preparation of 3a,21-diacet0xy-16a-methyl-17(20)- pregnen-I 1 -ol 6.8 g. of 1fiat-methyl-17(20)-pregnene-3u,1lfi,2-triol is acetylated overnight at room temperature in 18 m1. of

dry pyridine and 9 ml. of. acetic anhydride: The excess acetic anhydride is destroyed by the addition of 5 of: water. The reaction. mixture is poured into 100"mL-of On standing, methyl 3a -hydroxy- 16u methyl- 11 oxo- 17(20) pregnen-= The reaction mixture is stirred The ether is washed with 1 N hydrochloric acid followed hy dilute potassium carbonate, The dried ethereal solution (sodium carbon-- ate) is evaporated to'giv'e3 ,21-diacetoxy 16a methyl 17(20)-pregnen-11-ol as asolid glass. i

Preparation of 3d,21-diacet0xy-1Ifi,'17a-dihydr0xy- 16o -methyl-pregnart-20-0ne f 191 mgjof osmium tetroxide (19,1 ml." of a 1%"solution in anhydrous tertiary butyl alcohol) and 1.3 g. ofhydro-i' gen peroxide 16.5 ml. of a 2.31M solution anhydrous tertiary butyl alcohol). At the end of the reaction period a solution of 4.2 g. of sodium'sulfite in 190 ml. of water.

is added and the mixture stirred 30 minutes. The tertiaiy butanol is removed in vacuo and the residue extracted with methylene chloride. The dried methylene chloride extract on evaporation gave 5.53 g. of amorphous product 3e,11B,17a,2l-tetrahydroxy-16a-methylpregnan-ZO-one which is reacetylated at room temperature, overnight, with 25 ml. of dry pyridine and ml. of acetic anhydride. 'Ihe reagents are removed in vacuo and the residue dissolved in ether. The ether solution is washed with 1.25 N hydrochloric acid, water and saturated sodium bicarbonate solution. The dried (magnesium sulfate) ethereal solution on evaporation aflords 5.0 g. of crude 3a,21-diacetoxy-11fi,l7a-dihydroxy-16a-methylpregnan-ZO-one (Blue tetrazolium test positive).

The crude 3a,21-diacetoxy-11B,17a dihydroxy 16amethylpregnan-ZO-one is dissolved in 50 ml. of methylene chloride and chromatographed on 500 g. of Florisil. The column is eluted with methylene chloride-acetone mixtures. From the methylene chloride-2% acetone eluate the 3a,21-diacetoxy-11fl,17a-dihydroxy-l6a methylpregnan--one is obtained. Recrystallized from methanol the compound melted at 193.5-l97.5 C. The authenticity of the product was determined by infra-red spectra and paper strip chromatogram. Yield 0.31 g. (1 fraction only).

Preparation of 1 701,21dihydroxy-I6a-methyl-4- pregnene-3,I1,20-trione To a solution of 6 grams of crystalline N-bromo acetamide in 116 cc. of methanol, 1.8 cc. of pyridine and 6 cc. of water is added 7 grams of 3a,1lp,17a,21-tetrahydroxy- 16a-methylpregnan-20-one. The mixture is stirred for 16 hours at room temperature protected from light. At the end of this time, considerable crystallization has occurred and 2.1 cc. of allyl alcohol is added to discharge excess N-bromo-acetamide followed by 2.2 cc. of 6 N hydrochloric acid for neutralization of the pyridine. Crystallization is forced to completion by slow addition of 450 cc. of water. After aging the mixture in an ice bath for one hour, the crystalline product, 17a,2l-dihydroxy-16umethylpregnane-3,1l-dione, is recovered by filtration, washed with water, and dried.

Five grams of 17a,2ldihydroxy-Mot-methylpregnane- 3,11-dione is mixed with 25.0 cc. of acetic anhydride and 1.6 cc. of pyridine is added as a catalyst. The mixture is stirred at 50 C. for three hours at which time the heating bath is replaced by a cooling bath. While carefully controlling the temperature at 45-50" C., 4.5 cc. of water is mixed with 9.5 cc. of glacial acetic acid and is added slowly to decompose excess acetic anhydride. After stirring the mixture for one hour at 40-45 C. to insure complete reaction, 250 mg. of zinc dust is added; vigorous stirring is continued for one hour, at 40-45 C. to effect complete reduction of small amounts of unwanted bromo ketones. The excess zinc is removed by 6. not, 17 a,21-dihydroxy-16 z methylpregnane-3J 1,20-trione- 21-acetate was crystallized by careful addition of cc.-;; of water.

To 1 gram of 1"/ a,2 l-dihydroxy- 1 6e-methylpregnane- 3,11,20-trione 21-acetate dissolved in 20 ml. of chloroform and 22.5 mLof glacial acetic acid, at atemperature of 55 C., is added two drops of a 0.010 N solution of; dry hydrogen bromide in glacial acetic acid. ;T0 about 3.80 ml. of 0.010 N hydrogen bromide in glacial acetic acid, at 55.- C., is added 4.30 ml. of a solution containing 4 grams of bromine in chloroform, and the resulting solution is added, over about a 10-minute period, to the solution-of the st eroid, .while maintaining the reactionmixtureat about j;55 C. .The reaction mixture is allowed'to stand at 55 C. for about one-half hour; a so lution.containing25, grams of sodium acetate in 30 m1. of 'wateris added, an.d the resulting mixture is stirred for about 5 minutes. Five milliliters of water are thenadded, and the aqueous mixture is extracted with ethyl acetate. The ethyl acetate extract is washed with aqueous sodium bicarbonate solution to neutrality, then with water, dried, and the solvent is evaporated in vacuo. The residual material is dissolved in 20 ml. of acetone, and to the solution is added 2.5 grams of sodium bromide and 1 ml. of water. The resulting mixture is-heated under reflux for a period of about 5 hours, the reaction mixture is cooled, and the acetone is evaporated in vacuo. The residual material is extracted into ether, the ether extract is washed with water, dried, and the solvent is evaporated to a volume of about 10 ml.; petroleum ether is added to this solution, and the crystalline material which separates is recovered and dried to give approximately 4-bromo-17u,21-dihydroxy-l6a-methylpregnane-3,11,20-trione 21-acetate.

A mixture of 4.8 grams of semicarbazide, 4.8 grams of 4 bromo 16oz methylpregnane 17a,21 diol 3,11,20- trione 21-acetate and 6.0 ml. of ethanol is heated under reflux in contact with a nitrogen atmosphere for a period of about three days, and the reaction solution is evaporated to a small volume, diluted with water and the crystalline material recovered and purified by recrystallization from aqueous methanol to give 17a,21-dihydroxy 16a methyl 4 pregnene 3,11,20 trione 3,20 bissemicarbazone 21-acetate.

Five grams of 17u,21-dihydroxy-16a-methyl-4-pregnene-3,11,20-trione-3,ZO-bis-semicarbazone 21-acetate is dissolved in a mixture of 10.0 cc. of benzene and 10.0 cc. of 11.0 N methanolic potassiumhydroxide, and the solution is allowed to stand at room temperature for a period of about 10 minutes. The solution is then acidified with acetic acid, the benzene is evaporated in vacuo, and the residual material is recrystallized from ethyl acetate to give :,2ldihydroxy-16a-methyl-4-pregnene-3,l1,20-trione-3,20-bis-semicarbazone.

A mixture of 6 grams of 17a,21-dihydroxy-l6a-methylpregnene-3,l1,20-trione-3,20,-bis-semicarbazone, 2.0 ml. of dimethylformamide, 6.0 ml. of chloroform, and 15.0 ml. of 10.0 N aqueous hydrochloric acid is heated under reflux for a period of about three hours. The resulting two-phase system is cooled to a temperature of approximately 15 C., and the layers are separated. The aqueous layer is extracted with chloroform, and the chloroform extracts are combined with the original chloroformdimethylformamide solution. The combined organic layer is washed with an aqueous solution of sodium bicarbonate, and chloroform and dimethylformamide in the combined organic layer is replaced with ethyl acetate by evaporation in vacuo. Petroleum ether is added and the resulting solution is subjected to a partition chromatogram on diatomaceous earth using aqueous methanol as the stationary phase and benzene-chloroform as the moving phase to give 17a,2l-dihydroxy-16a-methyl-4-pregnene- 3 ,1 1 ,20-trione.

Various changes and modifications may be made in' filtration after cooling to room temperature and the prod- 75 this invention, certain preferred embodiments of which e o, r are herein disclosed,- without departing from the scope 6. The process which 'CQIIlPiiSBS Ieactingh-acetoxythereof; to the extent that these changes and modifications 110:,21 dibromo l ltimmethylpregnane-l1,20 dione with are within the scope of the appended claims, they are 1o alcoholic potassium hydroxide to form 3u-hydroxy-16ube considered as part of this invention. methyl-11-oxo-17(20} pregnen-21 oieacid;

1. 3oz acetoxy 17a,21-dibromo-16a-methylpregnane- References u male-file i this'patent ll' zzo-sdiolfind th v UNITED STATES'PATENTS zl-icgid y roxy 16oz me yl 11 oxo-17(20)pregnen- 2,752,366, egg T June 26 1956 3. Methyl 3a hydroxy-16a-methy1-11-oxo 17'(20)- 10' 2769824 Smneideret f 1956 WgHeH-ZI-Oate- OTHER REFERENCES 4. A process Whlch. comprises reactmg 3a-acetoxy-16a- V I J v methylpreguane-1L20-dione, with bromine to form" 3w i gg agg gg h' g'gj ghy q k -A et acetox 17 ,21 dibromo 16 -meth 1 re an -1"1','20- "Pages v diormy a a yP e I ourna1.0fAme 'ican Chemical Society vol 77 (1955),

. 5. A recess which com rises react 3 -h'dr l? byRosenktanzet'al" Page 2 fi flgLl1 17(zo g zl i i ig g fffi Fieser: Natural ProduetsReleted. to Phenanthrene,

azorhethane to form methyl 3a-hydroxyl-11-oxo-16a- 19'49Page Y methyl- 17 (20) -pregnen-21-oa.te. i i 

1. 3A - ACETOXY - 17A,21-DIBROMO-16A-METHYLPREGNANE11,20-DIONE. 